U.S. patent number 6,479,218 [Application Number 09/686,815] was granted by the patent office on 2002-11-12 for method for manufacturing multi-domain liquid crystal cell.
This patent grant is currently assigned to LG Philips LCD Co., Ltd. Invention is credited to Young Seok Choi.
United States Patent |
6,479,218 |
Choi |
November 12, 2002 |
Method for manufacturing multi-domain liquid crystal cell
Abstract
A method of manufacturing a multi-domain liquid crystal display
device having a pixel includes the steps of forming an alignment
film on at least one of a first and second substrate; covering the
alignment film with a mask, there being included a first surface
having a plurality of light-transmitting portions and
light-shielding portions and a second surface having
light-shielding portions corresponding to the light-transmitting
portions; radiating light from an upper portion of the mask; and
assembling the first and second substrates.
Inventors: |
Choi; Young Seok (Kumi-shi,
KR) |
Assignee: |
LG Philips LCD Co., Ltd (Seoul,
KR)
|
Family
ID: |
19615407 |
Appl.
No.: |
09/686,815 |
Filed: |
October 12, 2000 |
Foreign Application Priority Data
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|
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Oct 14, 1999 [KR] |
|
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1999-44621 |
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Current U.S.
Class: |
430/321; 349/124;
349/129; 430/396 |
Current CPC
Class: |
G02F
1/133753 (20130101); G02F 1/133788 (20130101); G02F
1/133761 (20210101) |
Current International
Class: |
G02F
1/1337 (20060101); G02F 1/13 (20060101); G02F
001/133 () |
Field of
Search: |
;430/321,396,20
;349/124,129 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
44 20 585 |
|
Jun 1994 |
|
DE |
|
197 03 682 |
|
Jan 1997 |
|
DE |
|
0 261 712 |
|
Mar 1988 |
|
EP |
|
0 525 473 |
|
Feb 1993 |
|
EP |
|
0 525 478 |
|
Feb 1993 |
|
EP |
|
0 611 786 |
|
Feb 1994 |
|
EP |
|
0 635 748 |
|
Jan 1995 |
|
EP |
|
0 708 354 |
|
Apr 1996 |
|
EP |
|
0 742 471 |
|
Nov 1996 |
|
EP |
|
0 750 212 |
|
Dec 1996 |
|
EP |
|
0 549 283 |
|
Jul 1997 |
|
EP |
|
0 788 012 |
|
Aug 1997 |
|
EP |
|
2 281 977 |
|
Mar 1995 |
|
GB |
|
2 286 893 |
|
Aug 1995 |
|
GB |
|
2 309 793 |
|
Aug 1997 |
|
GB |
|
2 309 794 |
|
Aug 1997 |
|
GB |
|
2 310 048 |
|
Aug 1997 |
|
GB |
|
2 317 964 |
|
Apr 1998 |
|
GB |
|
2 319 093 |
|
May 1998 |
|
GB |
|
64-60833 |
|
Mar 1989 |
|
JP |
|
1-251344 |
|
Oct 1989 |
|
JP |
|
1-251345 |
|
Oct 1989 |
|
JP |
|
2-55330 |
|
Feb 1990 |
|
JP |
|
2-298917 |
|
Dec 1990 |
|
JP |
|
3-36527 |
|
Feb 1991 |
|
JP |
|
3-120503 |
|
May 1991 |
|
JP |
|
3 241 311 |
|
Oct 1991 |
|
JP |
|
4-7520 |
|
Jan 1992 |
|
JP |
|
4-284421 |
|
Oct 1992 |
|
JP |
|
4-350822 |
|
Dec 1992 |
|
JP |
|
5-19208 |
|
Jan 1993 |
|
JP |
|
5-34699 |
|
Feb 1993 |
|
JP |
|
5-53513 |
|
Mar 1993 |
|
JP |
|
5-232473 |
|
Sep 1993 |
|
JP |
|
7-56173 |
|
Mar 1995 |
|
JP |
|
7-261185 |
|
Oct 1995 |
|
JP |
|
7-318861 |
|
Dec 1995 |
|
JP |
|
7-318942 |
|
Dec 1995 |
|
JP |
|
8-334790 |
|
Dec 1996 |
|
JP |
|
9-211465 |
|
Aug 1997 |
|
JP |
|
9-211468 |
|
Aug 1997 |
|
JP |
|
9-265095 |
|
Oct 1997 |
|
JP |
|
9-318946 |
|
Dec 1997 |
|
JP |
|
10-078584 |
|
Mar 1998 |
|
JP |
|
10-90684 |
|
Apr 1998 |
|
JP |
|
10-154658 |
|
Jun 1998 |
|
JP |
|
10-161126 |
|
Jun 1998 |
|
JP |
|
10-332932 |
|
Dec 1998 |
|
JP |
|
11-194344 |
|
Jul 1999 |
|
JP |
|
11-194345 |
|
Jul 1999 |
|
JP |
|
94/01754 |
|
Jan 1994 |
|
WO |
|
95/18189 |
|
Jul 1995 |
|
WO |
|
95/22075 |
|
Aug 1995 |
|
WO |
|
95/34843 |
|
Dec 1995 |
|
WO |
|
WO 96/22561 |
|
Jul 1996 |
|
WO |
|
99/08148 |
|
Feb 1999 |
|
WO |
|
Other References
Gibbons, "Nature" (Letters to Nature); vol. 351; pp. 49-50; May 2,
1991. .
Schadt et al., "Surface-Induced Parallel Alignment of Liquid
Crystals"; Jpn. J. Appl. Phys. vol. 31; pp. 2155-2164; Jul. 1992.
.
Yasufami Iimura et al.; "Alignment Control of a Liquid Crystal...";
Jpn. J. Appl. Phys.; vol. 32; pp. 93-96 (Jan.1993). .
Kunihiro Ichimura; "Nematic Liquid Crystal Alignment"; MCLC; pp.
998-1001, 1044; Oct.1993. .
Y. Toko et al.; "TN-LCDs Fabricated by Non-Rubbing Showing
Wide..."; SID 93 Digest; pp. 622-625. .
T. Sugiyama et al.; "Electro-Optic Characteristics of
Amorphous..."; SID 94 Digest; pp. 915-918. .
A. Lien et al.; "UV Modification of Surface Pretilt of Alignment
Layers..."; Appl. Phys. Lett. 67 (21) pp. 3108-3110,1598 (Nov.
1995). .
M. Schadt; "Investigation of the Mechanism of the Surface-Induced
Alignment..."; SID 95 Digest; pp. 528-531. .
J.L. West; "Polarized UV-Exposed Polyimide Films for Liquid-Crystal
Alignment..."; SID 95 Digest; pp. 703-705. .
T. Hashimoto; "TN-LCD with Quartered Subpixels Using Polarized...";
SID 95 Digest; pp. 877-800. .
T. Saitoh et al.; "A New Hybrid N-TB Mode LCD..." Asia Display '95;
pp. 589-592. .
A. Lien et al.; "UV-Type Two-Domain Wide Viewing Angle..."; Asia
Display '95; pp. 593-596. .
T. Yamamoto et al.; "Liquid Crystal Alignment..."; SID 96 Digest;
pp. 642-645 with 2 Cover Pages. .
M. Schadt et al.; Optical Patterning of Multi-domain...; Nature
vol. 381, pp. 212-215 (May 1996). .
J. Chen et al.; "Model of Liquid Crystal Alignment..."; The
American Physical Society; vol. 54 No. 2; pp. 1599-1603 (Aug.
1996). .
H.S. Soh et al.; "The Realization of Wide Viewing Angle..."; Euro
Display '96; pp. 579-582. .
J. Chen et al.; "Mechanism of Liquid Crystal Alignment..." SID 96
Digest, pp. 634-637. .
K. W. Lee et al.; "Late-News Poster: Mechanism of UV
Modification..."; SID 96 Digest; pp. 638-641. .
J. H. Kim et al.; "Late-News Poster: Photo-Alignment of Liquid
Crystals"; SID '96 Digest; pp. 646-647, 649. .
Y. Saitoh et al.; "Stability of UV-Type Two-Domain
Wide-Viewing-Angle..."; SID 96 Digest; pp. 662-665. .
D. S. Seo et al.; "Surface Alignment of Liquid Crystals in
LCDs..."; SID 93 Digest; pp. 954-956. .
Y. Iimura; "Prospects of the Photo-Alignment Technique..."; SID 97
Digest; pp. 311-314. .
R. Shashidhar et al.; "A New Non-Rubbing Technique..."; SID 97
Digest; pp. 315-318. .
M. Schadt et al.; "Optical Patterning of Multidomain LCDs..."; SID
97 Digest; pp. 397-400. .
K. Y. Han et al.; "A Study on the Photo-Alignment of the
Polymer-Containing..."; SID 97 Digest, pp. 707-710. .
F. Yamada et al., "A New Photo-Alignment Scheme for LC-Cell
Pretilt...", SID 97 Digest; pp. 715-718. .
M.S. Nam et al., "Wide-Viewing-Angle TFT-LCD..."; SID 97 Digest;
pp. 933-936. .
Jpn. J. Appl. Phys., "Molecular Orientations and Optical
Transmission Properties of Liquid Crystal Cells with Slit-Patterned
Electrodes," vol. 36 (1997) 1178-1184. .
Hasegawa et al., "Nematic Homogeneous Photo Alignment By Polyimide
Exposure to Linearly Polarized UV," J. of Photopolymer Science and
Technology, vol. 8, No. 2, pp. 241-248, 1995. .
Shannon et al., "Patterned Optical Properties in Photopolymerized
Surface-Aligned Liquid-Crystal Films," Nature, vol. 368, pp.
532-533, 1994..
|
Primary Examiner: McPherson; John A.
Attorney, Agent or Firm: McKenna Long & Aldridge,
LLP
Claims
What is claimed is:
1. A method for manufacturing a multi-domain liquid crystal display
device having a pixel comprising the steps of: forming an alignment
film on at least one of first and second substrates; covering the
alignment film with a mask, the mask including a first surface
having a plurality of light-transmitting portions and
light-shielding portions and a second surface having
light-shielding portions corresponding to the light-transmitting
portions of the first surface; irradiating light from an upper
portion of the mask; and assembling the first and second
substrates.
2. The method of claim 1, wherein the light-transmitting portions
and the light-shielding portions of the first surface are arranged
at constant interval.
3. The method of claim 2, wherein the arrangement interval of the
light-transmitting portions is identical with an arrangement
interval of the pixel.
4. The method of claim 2, wherein the arrangement interval of the
light-shielding portions is identical with an arrangement interval
of the pixel.
5. The method of claim 2, wherein the width of the
light-transmitting portions includes a half width of the
arrangement interval of the mask.
6. The method of claim 2, wherein the width of the light-shielding
portions includes a half width of the arrangement interval of the
mask.
7. The method of claim 1, wherein a distance d between the first
surface and the second surface of the mask includes d=w.times.tan
.theta. (w is a pattern width of the a mask and .theta. is an angle
of irradiation).
8. The method of claim 7, wherein the irradiation angle depends on
the distance d.
9. The method of claim 8, wherein a pretilt angle of the pixel
depends on the irradiation angle.
10. The method of claim 9, wherein the pretilt angle of the pixel
corresponding to the plurality of light-transmitting portions of
the first surface is different from the pretilt angle of the pixel
corresponding to the plurality of light shielding portions of the
second surface.
11. The method of claim 1, wherein a distance between the second
surface of the mask and the alignment film is a half of the
distance between the first surface and the second surface of the
mask.
12. The method of claim 1, wherein the mask includes a glass.
13. The method of claim 1, wherein the mask includes a quartz.
14. The method of claim 1, wherein the light includes ultraviolet
rays.
15. The method of claim 1, further comprising the step of forming a
liquid crystal layer between the first and second substrates.
16. The method of claim 1, wherein the step of irradiating includes
obliquely irradiating.
17. A method for manufacturing a multi-domain liquid crystal
display device having a pixel comprising the steps of: forming an
alignment film on at least one of first and second substrates;
irradiating light on the substrates using a mask including a first
surface having a plurality of first light-shielding portions, and a
second surface isolated from the first surface and having a
plurality of second light-shielding portions except for the first
light-shielding portions; and assembling the first and second
substrates.
18. The method of claim 17, wherein the first light-shielding
portions and the second light-shielding portions are formed at
constant intervals, respectively.
19. The method of claim 17, wherein the width of the first and
second light-shielding portions includes a half width of the
arrangement interval of the mask.
20. The method of claim 17, wherein a distance d between the first
surface and the second surface of the mask includes d=w.times.tan
.theta. (w is a pattern width of the a mask and .theta. is an angle
of irradiation).
21. The method of claim 20, wherein the irradiation angle depends
on he distance d.
22. The method of claim 21, wherein a pretilt angle of the pixel
depends on the irradiation angle.
23. The method of claim 22, wherein the pretilt angle of the pixel
corresponding to the first light-shielding portions is different
from the pretilt angle of the pixel corresponding to the second
light-shielding portions.
24. The method of claim 17, wherein a distance between the second
surface of the mask and the alignment film is a half of the
distance between the first surface and the second surface of the
mask.
25. The method of claim 17, wherein the mask includes a glass.
26. The method of claim 17, wherein the mask includes a quartz.
27. The method of claim 17, wherein the light includes ultraviolet
rays.
28. The method of claim 17, further comprising the step of forming
a liquid crystal layer between the first and second substrates.
29. The method of claim 17, wherein the step of irradiating
includes obliquely irradiating.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method or manufacturing a
multi-domain liquid crystal cell, and more particularly, to a
method for manufacturing a multi-domain liquid crystal cell in
which a liquid crystal cell of a multi-domain liquid crystal cell
having a wider viewing angle is obtained by a simple process.
2. Discussion of the Related Art
Recently, a liquid crystal display (LCD) mainly used for portable
televisions or notebook computers requires a large sized screen, so
as to be used for a wall type television or a monitor. A
twisted-nematic (TN) liquid crystal cell is generally used as an
LCD. The TN liquid crystal cell has different optical
transmittivity characteristics at each gray level depending on
viewing angles. For this reason, a large area of the TN liquid
crystal cell is limited. That is, optical transmittivity is
substantially symmetrical in view of a viewing angle in left and
right direction while optical transmittivity is asymmetrical in
view of us and down direction. Accordingly, an image inversion area
exists in the viewing angle in up and down direction. As a result,
there is a problem that the viewing angle becomes narrow. To solve
such a problem, there is suggested a multi-domain liquid crystal
cell in which a compensation effect of a viewing angle is obtained
by varying a main viewing angle in each pixel. To obtain the
multi-domain liquid crystal cell, a reverse rubbing process will be
described with reference to FIG. 1.
As shown in FIG. 1a, an entire substrate 11 on which a polyimide 12
is deposited is processed by rubbing. Thus, a mono-domain is formed
as shown in FIG. 1b. As shown in FIG. 1c, one domain is blocked by
a photoresist 13. Rubbing is then performed in a direction opposite
to the rubbing direction of FIG. 1a. As shown in FIG. 1d, a domain
which is not blocked by the photoresist 13 is processed by reverse
rubbing. As shown in FIG. 1e, if the photoresist 13 is removed, a
substrate divided into two domains having opposite pretilt angles
can be obtained.
However, the liquid crystal cell manufactured by the above rubbing
process has problems in that dust or static electricity occurs
during the rubbing process, thereby reducing yield or damaging the
liquid crystal cell.
In another related art, to solve such problems, photo-alignment
methods based on UV rays have been suggested instead of rubbing One
photo-alignment method will be described with reference to FIG. 2.
As shown in FIG. 2a, a substrate 21 on which an alignment film 22
is deposited is periodically shielded by a mask 23 having a
light-transmitting portion 25 and a light-shielding portion 24.
When light (solid line arrow in tilt direction on a top of the
drawing) is irradiated at a tilt at an angle of .theta., a first
pretilt is determined in a portion 26 where light is transmitted.
As shown in FIG. 2b, the mask 23 is rearranged to shield light in
the portion 26. Then, when light (solid line arrow in tilt
direction on a top of the drawing) is irradiated at a tilt at an
angle of -.theta., a second pretilt is determined in a portion 27
where light is shielded in FIG. 2a. Thus, as shown in FIG. 2c, a
first substrate of two domains having different pretilts can be
obtained. Also, as shown in FIG. 2d, a second substrate of two
domains can be obtained by the above alignment method and lower and
upper substrates are assembled with each other.
Furthermore, as shown in FIG. 3, areas Q and R are light-shielded,
and the photo-alignment methods having an angle .theta. of
irradiation in FIGS. 2a and 2b are sequentially applied to areas O
and P as shown in FIGS. 3a and 3b. The areas O and P are then
light-shielded, and the photo-alignment methods having an angle
.theta. of irradiation in FIGS. 2a and 2b are sequentially applied
to the areas Q and R as shown in FIGS. 3c and 3d. Thus, light
irradiation of total four times is performed on the substrate,
thereby obtaining a substrate having four domains.
As described above, the first substrate and the second substrate in
which four domains are formed are bonded to face each other and
then the liquid crystal is injected thereto, so that a four-domain
liquid crystal cell can be obtained.
In still another related art, as shown in FIG. 4a, a
semi-transparent portion 43 of a mask is arranged in some area of a
substrate 41 on which an alignment film 42 is deposited, and then
light irradiation is performed. Thus, the irradiated light is
absorbed in the alignment film 42 on the substrate 41 in an
aperture portion. However, some of the irradiated light is only
absorbed in the alignment film 42 in an area of the alignment film
42 of the substrate 41 corresponding to the semi-transparent
portion 43 of the mask. Polysiloxane based materials used as the
alignment film 42 are characterized in that the size of tie pretilt
angle becomes small as absorbing light energy increases.
Accordingly, the size of the pretilt angle formed in the alignment
film can easily be controlled. Based on this characteristic, a
substrate having different pretilt angles and divided pixels is
manufactured, and a sectional view of the substrate is shown in
FIG. 4b. As shown in FIG. 4c, a liquid crystal cell is manufactured
in such a manner that upper and lower substrates are bonded to
each, other by applying the substrate of FIG. 4b. In this
structure, alignment direction of each domain is identical in each
substrate but the size of the pretilt angle is different.
Accordingly, a multi-domain is formed to improve a viewing angle.
Also, in case that the divided pixels are applied, a four domain
liquid crystal cell can be obtained as shown in FIG. 5. In this
case, areas III and IV are light-shielded and the photo-alignment
method of FIG. 4a is applied to areas I and II (see FIGS. 5a to
5d). Subsequently, the areas I and II are light-shielded, and in
the areas III and IV, a four-domain substrate is obtained by
varying polarization direction of tie irradiated light in the
photo-alignment method of FIG. 4a (see FIGS. 5e to 5h) . After the
first and second substrates in which four domains are formed are
bonded to each other by the above method, the liquid crystal is
injected into the substrates so as to obtain a four-domain liquid
crystal cell.
However, the methods for manufacturing a liquid crystal cell
through the photo-alignment methods have several problems in
controlling alignment direction of the multi-domain to realize a
wider viewing angle.
The first method requires light irradiation of eight times
(vertical irradiation of four times and tilt irradiation of four
times) into the upper and lower substrates to form a multi-domain
divided into two pixel areas, and mask bond no process of four
times. Moreover, to form a multi-domain having four domains, the
process steps increase two times. Thus, in addition to light
irradiation and mask bonding processes of several times, a cap
between the masks and the substrate should additionally be
controlled. These process steps are unattractive in view of the
mass production. The second method requires light irradiation of
four times (vertical irradiation of two times and tilt irradiation
of two times) into the upper and lower substrates and mask bonding
process of two times when forming a multi-domain having two
domains. In the second method, the light irradiation and the mask
bonding process steps have been reduced but error may occur in
arranging a number of masks, thereby reducing the productivity.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a method for
manufacturing a multi-domain liquid crystal cell that substantially
obviates one or more of the problems due to limitations and
disadvantages of the related art.
An object of the present invention is to provide a method for
manufacturing a multi-domain liquid crystal cell fin which a photo
mask required for photo-alignment is improved to perform tilt
irradiation having two different directions by irradiation of one
time, so that alignment division of a unit pixel can be realized
and a multi-domain liquid crystal cell can be obtained by a simple
process.
Another object of the present invention is to provide a method for
manufacturing a multi-domain liquid crystal cell in which the
number of masks is reduced to reduce error that may occur in
arranging the masks due to control of a gap between the masks and
the substrate.
Additional features and advantages of the invention will be set
forth in the description which follows, and in part will be
apparent from the description, or may be learned by practice of the
invention. The objectives and other advantages of the invention
will be realized and attained by She scheme particularly pointed
out in the written description and claims hereof as well as the
appended drawings.
To achieve these and other advantages and in accordance with the
purpose of the present invention, as embodied and broadly
described, a method for manufacturing a multi-domain liquid crystal
display device having a pixel comprising the steps of: forming an
alignment film on at least one of first and second substrates;
covering the alignment film with a mask, the mask including a first
surface having a plurality of light-transmitting portions and
light-shielding portions and a second surface having
light-shielding portions corresponding to the light-transmitting
portions of the second surface; irradiating light from an upper
portion of the mask; and assembling the first and second
substrates.
It is to be understood that both the foregoing general description
and the following detailed description are exemplary and
explanatory and are intended to provide further explanation of the
invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described in detail with reference to the
following drawings in which like reference numerals refer to like
elements wherein:
FIG. 1 shows a process for manufacturing a two-domain liquid
crystal cell according to a related art rubbing method;
FIG. 2 shows a process for manufacturing a two-domain liquid
crystal cell according to a related art photo-alignment method;
FIG. 3 shows a process for manufacturing a four-domain liquid
crystal cell according to a related art photo-alignment method;
FIG. 4 shows a process for manufacturing a two-domain liquid
crystal cell according to a related art another photo-alignment
method;
FIG. 5 shows a process for manufacturing a four-domain liquid
crystal cell according to a related art another photo-alignment
method;
FIG. 6 shows a process for manufacturing a two-domain liquid
crystal cell according to a photo-alignment method using a mask of
the present invention; and
FIG. 7 shows a process for manufacturing a four-domain liquid
crystal cell according to a photo-alignment method using a mask of
the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Reference will now be made in detail to the preferred embodiments
of the present invention, examples of which are illustrated in the
accompanying drawings.
FIG. 6 shows a process for manufacturing a two-domain liquid
crustal cell in which a pixel is alignment divided by UV
irradiation of one time using a mask. Referring to FIG. 6, an
alignment film 62 is deposited on a substrate 61. A plurality of
firs and second light-transmitting portions 64a and 64b and
light-shielding portions 63 are arranged at constant intervals on a
first surface 65 of the substrate 61 on which the alignment film is
deposited.
A mask 67 is arranged on a second surface 66 in such a manner that
the light-shielding portion is arranged in a position corresponding
to the light-transmitting portion of the first surface 65 and the
light-transmitting portion is arranged in a position corresponding
to the light-shielding portion. Then, UV irradiation is performed
using the mask 67 as shown in a tilt solid arrow on a top of FIG.
6. As shown in FIG. 6, the light irradiated to the first
light-transmitting portions 64a is obliquely irradiated at an angle
of .theta. in a direction of arrow x so that the light is absorbed
in a first domain of the alignment film 62 on the substrate 61. The
light irradiated to the second light-transmitting portions 64b is
tilt irradiated at an angle of -.theta. in a direction of arrow y
so that the light is absorbed in a second domain of the alignment
film 62 on the substrate 61. Accordingly, two different tilt
irradiation steps are performed by irradiation of one time to
alignment-divide a unit pixel, so that a liquid crystal cell having
simply divided domains can be manufactured. At this time, since the
size of the pixel is defined as shown in FIG. 5, the following
conditions should be satisfied. p.sub.1 (mask pattern
period)=p.sub.2 (pixel pitch) w(mask pattern width)=p.sub.1 /2
d(distance between the first surface and the second surface of the
mask)=w x tan .theta. (.theta. is an angle of irradiation)
g(distance between the second surface of the mask and the alignment
film)=d/2.
In the above conditions, the mask pattern period is an arrangement
period of the light-transmitting portion or the light-shielding
portion of the mask, the pixel pitch is an arrangement period of
the pixel, and the mask pattern width is a width of the
light-transmitting portion or light-shielding portion.
The liquid crystal cell can be manufactured by applying the
photo-alignment method of FIG. 6 to the upper and lower
substrates.
In the above pixel division method, the irradiation angle can be
controlled variously by varying the distance between the first
surface and the second surface based on w .times.tan .theta.. If
the irradiation angle is varied, the size of the pretilt angle in
each domain of the substrate is varied. Accordingly, the viewing
angle between neighboring domains is compensated, so that the
multi-domain liquid crystal cell can be obtained by the simple
process.
FIG. 7 shows a method for forming a four-domain liquid crystal cell
by applying the above method. That is, referring to FIG. 7a, a
first area A filled with dots on the substrate on which the
alignment film is deposited is covered with the above mask while a
second area B filled with oblique lines is covered with an opaque
mask. In this case, as shown in FIG. 6, the first light irradiation
of UV (solid line arrow on a top in the drawing) is performed at an
angle of .theta. to alignment-divide one pixel. Thus, a pretilt is
formed by the first light irradiation as shown in FIG. 7a. In FIG.
7a, the left arrow of the first area A denotes a pretilt direction
generated by UV in direction y passed through the second
light-transmitting portion 64b, i.e., UV irradiated at an angle of
-.theta., while the right arrow of the first area A denotes a
pretilt direction generated by UV in direction x passed through the
first light-transmitting portion 64a, i.e., UV irradiated at an
angle of .theta.. A pretilt is not formed in the second area B of
the alignment film corresponding to the opaque portion having
optical transmittivity of 0%. However, two domains having different
pretilt directions are formed in the area covered with the mask.
Next, as shown in FIG. 7b, the first area A in which the pretilt is
determined is covered with the opaque mask while the second area A
is covered with the mask 67 having the distance d' between the
first surface 65 and the second surface 66. In this case, since the
irradiation angle is varied to .theta. due to the variation from d
to d' of the distance between the first surface 65 and the second
surface 66, the second light irradiation (solid arrow on a top of
the drawing) can be performed in the second area B to have a
pretilt angle different from that of the first area A. Thus, a
pretilt is formed by the second light irradiation as shown in FIG.
7b. In FIG. 7b, the left arrow of the second area B denotes a
pretilt direction generated by UV in direction y passed through the
second light-transmitting portion 64b, i.e., UV irradiated at an
angle of -.theta., while the right arrow of the second area B
denotes a pretilt direction generated by UV in direction x passed
through the first light-transmitting portion 64a, i.e., UV
irradiated at an angle of .theta.. Since the second light
irradiation is blocked by the mask in the first area A of the
alignment film corresponding to the opaque portion having optical
transmittivity of 0%, the pretilt formed by the first irradiation
remains in the same manner as FIG. 7a. In case of the varied
distance d' between the first surface 65 and the second surface 66,
two domains having pretilt directions different from the first area
A are formed in the second area B covered with the mask, so that
the pixel is divided into four (see FIG. 7c).
If the four-domain substrate obtained by the above method is
applied to the upper and lower substrates, the main liquid crystal
cell of FIG. 4 can be formed.
As aforementioned, the method for manufacturing a multi-domain
liquid crystal cell has the following advantages.
In the present invention, the light-transmitting portions and the
light-shielding portions are arranged on the first surface at
constant intervals, and the photo-alignment is performed using the
mask which is formed in such a manner that the light-shielding
portions are arranged in a position corresponding to the
light-transmitting portion of the first surface and the
light-transmitting portions are arranged in a position
corresponding to the light-shielding portion. Accordingly,
alignment division of the unit pixel can be realized by irradiation
of one time and the number of the manufacturing process steps can
be reduced. Furthermore, since alignment division of the pixel is
realized by one mask, the steps of arranging a number of masks are
reduced. Thus, error that may occur in arranging the masks is
reduced, so that reliability of the alignment is improved, thereby
improving the productivity and lowering the production cost in case
of mass production.
The foregoing embodiments are merely exemplary and are not to be
construed as limiting the present invention. The present teachings
can be readily applied to other types of apparatuses. The
description of the present invention is intended to be
illustrative, and not to limit the scope of the claims. Many
alternatives, modifications, and variations will be apparent to
those skilled in the art.
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